This invention relates to monostable multivibrator circuits. More particularly, it relates to a monostable multivibrator circuit of the non-saturated type in which a signal amplifying transistor constituting the monostable multivibrator circuit operates in a non-saturated state.
A signal amplifying transistor in a monostable multivibrator circuit effects saturated operation when its collector potential has become lower than its base potential. At such time the current gain of the transistor lowers, and the change of the collector current responsive to the change of an input signal becomes small. Therefore, a current of an abrupt change corresponding to the input signal cannot be applied to a load of the transistor, and the rectangular waveform of an output signal becomes rounded. On account of the saturation, carriers are accumulated in a collector region and a base region of the transistor, so that the delay time of the output signal becomes comparatively long.
In order to avoid the drawbacks, the signal amplifying transistor may be operated in the non-saturated state by setting the lowest value of the collector potential to be higher than the base potential in advance. In this case, the output signal presents a favorable change free of influences by the lowering of the current gain or the accumulation of the carriers as described above.
However, in case where the signal amplifying transistor is operated in the non-saturated state in this manner, the operating range is determined by the characteristics of circuit elements, and hence, the circuit operation is greatly affected by dispersions in the characteristics of the circuit elements.
In semiconductor integrated circuits, the dispersions of the circuit elements are comparatively wide. When considering the construction of the monostable multivibrator with a semiconductor integrated circuit, therefore, it is feared that the saturated operation will occur due to the dispersions even when the constants of the circuit elements are set so as to establish the non-saturated operation.